Hirobo HI2509013 Needle Pin 4 x 21 for helicopter general parts  [HI2509013]

Needle pin for helicopter linkages

This Hirobo HI2509013 needle pin is an RC-scale replacement part intended for general helicopter assemblies. The listing identifies the part as a 4 x 21 needle pin used within Hirobo helicopter general parts, and it serves as a straightforward mechanical fastener in small linkage and pivot locations.

In practice this pin stabilizes connections such as rotor linkages and small control link pivots, helping to reduce axial play that can affect control feedback. When inspecting a model, check the seating and alignment of the pin and surrounding holes to maintain smooth control movement; replace if wear or deformation appears.

Installation is typically a press-fit into a locating bore or retained in place by the model's existing retainers, the pin acting as a simple locating and pivot element rather than a threaded fastener. For tuning, minimal axial clearance at the pin location can reduce slop but avoid excessive preload that could bind moving parts.